1. Field of the Invention
The present invention relates to a mobile terminal in a mobile communication system, and more particularly, to a system and method of controlling a multimedia call in a mobile communication system.
2. Background of the Related Art
Mobile terminals for providing a voice service are common. Use of Portable Computers (PCs) is rapidly spreading because of the cost decline of information and communication instruments. Thus, a mobile communication system currently receives requests of a radio data service in which a mobile telephone network is accessed using the mobile terminals and the portable PCs, and then a communication function is performed therebetween.
Such a mobile communication system sets up a data call between visual terminals via an Inter-Working Function (IWF) or a Public Data Serving Node (PDSN) for modem emulation or packet network access. In other words, the visual terminal in the mobile communication system is call-processed based upon a data service.
A system and method for controlling a data call in a mobile communication system of a related art communication terminal will now be described. FIG. 1 is a diagram that shows a method for connecting the data call in the related art mobile communication system. FIG. 2 shows a protocol for connecting the data call in the related art mobile communication system.
As shown in FIG. 1, a system for connecting the data call has a Mobile Station (MS) 101 for originating/receiving a radio data and a Base Station/Base Station Controller (BS/BSC) 102 for relaying the radio data of the MS 101 in local units. A Mobile Switching Center (MSC) 103 is for setting up a communication path according to a communication service requested from the MS 101. An Inter-Working Function (IWF) or a Packet Data Serving Node (PDSN) 104 is connected to the MSC 103 for performing a modem pool function for data service calling and internet access. A Public Switched Telephone Network (PSTN) 105 is for data communication and is connected to a data Mobile Terminal (MT) 106.
The MSC 103 processes a mobile call, inter-works to a subscriber information-processing unit, manages a visiting subscriber, processes a data call with the IWF and inter-works to other networks such as the PSTN/PCS. The IWF matches the transmission speed between the mobile telephone network and the PSTN and performs a modem pool function, and the PDSN allows the MS 101 to use a mobile Internet Protocol (IP) service after Point-to-Point Protocol (PPP) connection.
As shown in FIG. 2, the MS 101 and the BS 102 use the Radio Link Protocol (RLP) for originating/receiving a reliable data in a radio section, and an interval between the MS 101 and the IWF or PDSN 104 is connected by a PPP frame.
As shown in FIGS. 1 and 2, the MS 101 sets up the RLP with the BS/BSC 102 during conversation. When the RLP is set up, the PPP is set up with the IWF or PDSN 104 through the MSC 103.
The RLP is an NAK (Negative Acknowledge)-based protocol that is devised according to a scheme for reducing an error rate occurring in data transmission considering the features of the radio section. Examples of NAK-based protocol include the RLP1 for the IS-95A, the RLP2 for the IS-95B and the RLP3 for the IS-2000.
Further, as shown in FIG. 2, a relay layer is set up between the BS/BSC 102 and the MSC 103 and between the MSC 103 and the IWF or PDSN 104 in order to set up a PPP call. In other words, the relay layer is an IS-95 series layer for an air interface, which is described in standards such as IS-707, sets up the PPP call in a counterpart data MT 106 connected to the MS 101 and produces the data call via a specific number.
As a procedure for setting up a service call from the MS 101, upon data transmission from the MS 101 to the RLP, the BS/BSC 102 converts a received data into a type of internal message, and then the BS/BSC 102 transmits the converted data to the IWF 104 via the MSC 103. In sequence, the IWF 104 extracts a pure data from the received message and transmits the pure data to the data MT 106 via the PSTN 105. Data generated from the data MT 106 is transmitted in the same manner but in an inverse sequence from the PSTN 105 via the IWF 104.
The IWF 104 also performs a function of connecting to the PSTN 105 for a packet service. Thus, the IWF L04 uses the PPP in the link layer for connection with the internet network in the MS 101.
As described above, the related art mobile communication system has various disadvantages. In such a related art mobile communication system, a service should be used with one of a call service for data or the packet service for mutually connecting the visual display terminals.
Further, according to a line switching scheme in the related art mobile stations, one station should be set up in a modem-responding state and then another station modem-accesses to the counterpart. This line switching scheme can be currently performed up to 14.4 Kbps, but is required to use the IWF or the PDSN for a packet mode data service, which incurs problems of system load and delay.
In other words, since the IP of the mobile station is dynamically allocated and the IP can be allocated differently in every access when the mobile station uses the packet service option, it is difficult to set up a bidirectional call via IP in the related art mobile communication system. Also, since the related art mobile communication system necessarily passes through the IWF or PDSN for processing the multimedia call, there are problems of system load and delay.
Further, since the IWF or PDSN passes through a PPP/TCP stack when setting up the call between the visual terminals in the related art mobile communication system, there is a problem of a transmission delay because of the delay in a call processing or transmission of data during a call connection. Such transmission delay is fatal to the visual terminal that takes a real-time processing. Also, when the visual terminal is generalized, the visual terminal in the same network may unnecessarily pass through the IWF or the PDSN for connection, which creates overload.
In addition, when initiating the data call between the each mobile station and the base station, the service time point can be mismatched in the view of a higher application protocol because of a difference in time points of call establishment at both terminals, and thus unnecessary data can be transmitted. In other words, the receiving station responds when a certain time period elapses after the traffic channel is established between the originating station and the base station, so that the inconsistency takes place in the data exchanging time points between the both terminals after the traffic channel is opened between the base station and the receiving terminal. Accordingly, there is a problem that the receiving station may unnecessarily transmit the multimedia data of the originating station to the base station before call setup so that the multimedia protocol in the station can malfunction.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.